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Fundamentals Of The Living Cell > The cell cycle > Flashcards

The cell cycle Flashcards

1
Q

What are duplicated in the cell cycle and divided into?

A

DNA, organelles, cytoplasm

and divided into daughter cells

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2
Q

How many organisms does the cell cycle give rise to?

A

2 new organisms

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3
Q

What must the zygote undergo?

A

A zygote must undergo many rounds of the cell cycle to make a new fully grown organism

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4
Q

What must multicellular organisms like humans fo during their lifetime?

A

Must also constantly replace any cells that die during the lifetime of the organism

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5
Q

What is not possible with nerve cells

A

Nerve cells cell cycle re-entry is not possible

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6
Q

What happens to hepatocytes in the cell cycle?

A

Maintained in G0 unless stimulated to divide

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7
Q

What are epithelial and haematopoietic cells in?

A

Constantly in the cell cycle

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8
Q

What does FACS analysis show regarding DNA content during the cell cycle?

A

FACS analysis allows us to see that DNA content is greatest during the G1 phase and the lowest during the S phase

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9
Q

G1

A

Growth and preparation for S phase

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10
Q

S

A

Chromosome duplication

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11
Q

G2

A

Growth and preparation for M phase

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12
Q

what steps is interphase made up of?

A

G1+S+G2

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13
Q

What steps is the M phase made up of?

A

Made up of Mitosis and cytokenesis

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14
Q

Prophase

A

Chromosomes condense
Centrosomes move to opposite poles
Mitotic spindles form

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15
Q

Prometaphase

A

Nuclear envelope breakdown

Chromosomes attach to the mitotic spindle

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16
Q

Metaphase

A

Centrosomes are at opposite poles

Chromosomes are at there most condensed and line up at the equator of mitotic spindle

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17
Q

Anaphase

A

Sister chromatids separate

Each new daughter chromosome move to opposite spindle pole

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18
Q

Telophase

A

Chromosomes arrive at the spindle poles
These chromosomes expand
Nuclear envelope forms

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19
Q

What occurs in Cytokenesis?

A

Cytoplasm divides

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20
Q

What is the mitotic spindle?

A

Bipolar array of microtubules

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21
Q

When do mitotic spindles start assembling and from where?

A

Start assembling during prophase from the centrosomes at each pole

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22
Q

How do mitotic spindle attach to chromosome?

A

Attach to the chromosomes via the kinetochore

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23
Q

What do mitotic spindles do

A

Pull apart the sister chromatids

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24
Q

What are the 3 types of spindle fibres

A

Astral microtubules
Kinetochore microtubules
Interpolar microtubules

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25
Q

What is the Kinetochore?

A

A protein structure formed on a chromatid, where the spindle fibres attach and pull the chromatids apart during cell division

26
Q

What is the centromere?

A

a part of the chromosome connected to the spindle fibre

27
Q

What are chromatids?

A

the two chromosomes that have been replicated and linked through the centromere

28
Q

What organising centre is there in somatic animal cells?

A

In somatic cells, microtubule organising centre is present

29
Q

What do centrosomes consist of and what is it surrounded by?

A

Centrosomes consists of a pair of centrioles surrounded by pericentriolar matrix

30
Q

When are centrioles replicated?

A

Replicated during interphase

31
Q

What do centrioles do to prepare for M phase?

A

Migrate to opposite poles in preparation for M phase

32
Q

What stage is cytokenesis in the cell cycle?

A

Final step in the cell cycle

33
Q

What does cytokinesis do?

A

Divides the cytoplasm into two daughter cells

34
Q

What is the contractile rings structure?

A

Cytoskeletal structure composed of actin and myosin bundles

35
Q

Where do the actin and myosin bundles in contractile rings accumulate?

A

Accumulate between the poles of the mitotic spindle beneath the plasma membrane

36
Q

What does the contractile ring do and form?

A

Ring contracts and forms an indentation or cleavage furrow, dividing the cell in two

37
Q

How do cell organelles regenerate?

A

Cell organelles spontaneously regenerate so must be already present in the new daughter cells.

38
Q

Mitosis overview

A

§ Two cells
§ Diploid
§ Cells divide once
§ No recombination between homologous chromosomes

39
Q

Meiosis overview

A

§ Four cells
§ Haploid
§ Cell divide twice

Homologous recombination occurs

40
Q

What does meiosis start and end with?

A

Division which starts with one diploid cell and ends with 4 haploid cells

41
Q

What does meiosis produce

A

Sperm and Egg cell

42
Q

Steps of mitosis

A

○ First there’s a round of DNA replication during the S phase to double the genetic content
○ Meiosis one:
§ Homologous chromosomes line up on the spindle and then separate to opposite spindle poles
○ Meiosis two:
§ Sister chromatids line up on the spindle and separate to opposite spindle pole
Recombination occurs between homologous chromosomes

43
Q

What is Nondisjunction?

A

Failure of homologous chromosomes to separate from one another either at meiotic division one or meiotic division 2.

44
Q

What happens when non-disjuncton occurs in autosomes?

A 
§ If in autosomes, usually fatal however there are a few exceptions:
        Trisomy 21(Downs syndrome)
45
Q

What happens when nondisjuntion occurs in sex chromosomes?

A

XO(turners syndrome)

46
Q

What regulation of the cell cycle is required?

A

○ Entry into the cell cycle must be strictly controlled
○ Each phase must only occur only once per cycle
Phases must be in the correct order and non overlapping

47
Q

What are the G1 checkpoints in the cell cycle?

A 
§ Check extracellular environment, growth factors, mitogenic signals and check for DNA for damage
§ Induction/expression of cyclin D
§ Binding/activation of Cdk4
§ Phosphorylation of pRB
§ Release and activation of E2F

S phase gene transcription

48
Q

How is DNA damage repaired?

A

□ Normal p53 degrades very quickly, is unstable and maintained at very low levels
□ Phosphorylated p53 is not degraded
□ Active p53 promotes the transcription of the p21 gene that induce cell cycle arrest by binding to the promoter region of p21
□ P21 binds and inhibits G1/S-Cdk and S-Cdk complexes

Causing cell cycle arrest which gives more time to repair damaged DNA

49
Q

What are the G2 checkpoints in the cell cycle?

A

Check DNA replicated properly, check for DNA damage

50
Q

What are the metaphase checkpoint?

A

Are all chromosomes aligned on the mitotic spindle

51
Q

What are the two main cell cycle regulators?

A

Cdks and cyclins

52
Q

How do Cdks regulate cell cycle?

A

§ Enzymes which phosphorylate the target proteins

Become active when bound to a corresponding cyclin

53
Q

How do cyclins regulate cell cycle?

A

§ Regulators of Cdks

§ Different cyclins are produced at each phase of the cell cycle

54
Q

What are the levels of cdks and cyclin throughout the cell cycle?

A

Cdk levels fairly stable

Cyclin levels vary

55
Q

What does cdk bound to cyclin do?

A

Cdk bound to cyclin is active and can phosphorylate target protein

56
Q

What does cdk activation trigger?

A

Cdk activation triggers the next step in the cell cycle such as entry into S phase or M phase

57
Q

What does Cyclin degradation do?

A

Cyclin degradation terminates Cdk activity

58
Q

Give two examples of cyclin dependant kinase inhibitors

A

INK4 and CDK inhibitory protein

59
Q

What does INK4 do

A

Inhibits G1 CDK’s

60
Q

What do CDK inhibitory proteins do?

A

Inhibit all other CDK-cyclin complexes gradually sequestered by G1 CDKs thus allowing activation of later CDKs.

Fundamentals Of The Living Cell (31 decks)

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